This invention relates to a gas turbine engine stator vane assembly and in particular to a vane assembly having an effective flow area which is variable.
Modern ducted fan gas turbine engines conventionally have two or three shafts interconnecting the various rotary components of their compressors and turbines. It is desirable to vary the work distribution between these shafts in order to ensure efficient engine performance over a wide range of operating conditions. Such work distribution between the engine shafts is principally governed by the effective flow areas of the individual engine turbines. Similar requirements apply to multishaft gas turbines providing shaft drive.
It has been proposed to vary the turbine effective flow areas by the use of stator guide vanes which are rotatable about their longitudinal axis. However with such vanes, great difficulty is usually encountered in achieving an effective gas seal between the rotatable vane portions and the static portions adjacent those rotatable portions. Additionally, turbine components are subject to high aerodynamic and mechanical loads. This makes it very difficult to provide actuating mechanisms which are capable of providing effective vane rotation with sealing whilst being acceptably robust and light in weight.
It has also been proposed to use jets of cool air to obstruct the areas between adjacent stator guide vanes. However these have been found to bring about unacceptable performance penalties.